This invention relates to resuscitators, parts and assemblies.
Resuscitators are used to ventilate a patient who is not breathing voluntarily. One type of resuscitator has a resilient squeeze bag that is squeezed by hand to administer air to a patient via a face mask, an endotracheal tube, laryngeal mask or the like. The resuscitator has a valve arrangement that directs air to a patient outlet coupling when the bag is squeezed and allows exhaled gas from the patient to flow directly to an exhaust outlet. The valve arrangement also allows air back in to refill the bag when it is released after having been squeezed. Where the resuscitator is used with an endotracheal tube it is important that checks are made to ensure that the tube is correctly placed, that is, to ensure it is in the trachea and not in the oesophagus. One way in which this can be done is by means of a carbon dioxide indicator since carbon dioxide is produced as a result of respiration and the level of this gas from the lungs significantly exceeds that in atmospheric air and in gas from the oesophagus. Hence, a low level of carbon dioxide is indicative of incorrect intubation. Carbon dioxide levels can be monitored in a well-equipped hospital with a capnograph. Alternatively, an indicator formed from a calorimetric substance could be used, usually in the form of a treated paper strip. The indicator can be connected directly to the endotracheal tube or, as proposed in U.S. Pat. No. 4,790,327, it can be incorporated into the exhaust outlet of the resuscitator. Resuscitators of this kind are sold by Nellcor of California, USA under the name Indgo. It is desirable for such indicators to be highly visible and reliable in their response. Other patents describing carbon dioxide indicators used with resuscitators include U.S. Pat. No. 5,749,358 and U.S. Pat. No. 6,058,933.
Alternative resuscitators have a source of air or oxygen, such as from a compressed gas cylinder, connected to a mechanical valve and regulator arrangement by which the user can supply gas to the patient. An example of such a resuscitator is described in GB 2282542. It is also desirable with this form of resuscitator, where it is connected to an endotracheal tube to be able to check that the tube has been correctly positioned in the trachea. It can also be desirable to check that the patient is breathing correctly when a resuscitator is used with a face mask or a laryngeal mask.